The present invention relates to heaters for heating steering wheels for vehicles, heater-equipped steering wheels, and a method of manufacturing such steering wheels.
When using the steering wheels for vehicles in cold conditions such as the outdoors in winter, it is desirable for comfortable steering after vehicle start to quickly heat a steering-wheel rim up to a temperature suitable for driver""s holding operation.
One solution is to heat the steering-wheel rim by means of engine coolant or hot air out of an air-conditioning box. However, for cooled vehicles in cold conditions such as the outdoors in winter, this solution needs sufficient warming-up of the vehicles, leading to difficulty of quick heating of the rim.
Another solution is to arrange in a grip portion of the steering wheel a sheet-like heater to which engine-generated power is supplied.
JP-Y2 63-11029 discloses a heater-equipped steering wheel comprising a steering-wheel main body having a heat insulator at the outer periphery, a sheet-like heating unit placed on the heat insulator, and a covering placed on the heating unit. The heating unit comprises a covered heater wire having a core string and a heating wire wound thereon, which is disposed zigzag and close on the inner surface of a heat-equalizing aluminum foil. However, the zigzag arrangement of the heater wires on the foil needs complicated operation when visually excellently mounting the heating unit along the rim of the annular steering wheel having circular section, leading to difficult enhancement in workability. In other words, the provision of finished products having excellent appearance involves an increase in manufacturing cost. Moreover, the zigzag arrangement often creates protrusion of thick heater wires on the covering, i.e. so-called outstanding state thereof, which can be perceived visually and tactilely, resulting in difficult enhancement in visual quality and operation feel of the steering wheel.
JP-A 4-15162 discloses a heatable steering wheel including a net heating insert obtained by weaving a plurality of thin heating wires. The heating insert is connected to a covering material by means of joining or other appropriate means, which is mounted to a steering-wheel main body. This allows deformation of a heater in response to the curved surface of the steering-wheel rim in securing the amount of generated heat per unit area. This structure is preferable in view of difficulty of creating the so-called outstanding state of the heater wires. However, mounting the band-like net heater along the surface of the rim is not easy operation exactly. Moreover, preforming the net heater to conform to the shape of the rim involves an increase in manufacturing cost and a decrease in general versatility. Furthermore, as is not apparent from the disclosure of JP-A 4-15162, when fixing the net heater by full application of an adhesive, stress acts concentratedly on fixed areas to bring easy breaking of the heater wire. And when having relatively small number of heater wires, breaking of some heater wires can lower the heater capacity, so that prudent assembling is needed not to damage the heater wires, causing lowering of the workability and yield or necessity of careful inspection, leading to difficult reduction in manufacturing cost. Particularly, feed portions located at both ends of the heater wherein an expandable net heating portion and feeders are connect to terminal plates can concentratedly undergo tensile stress during assembling, forming a cause of breaking of the heater wires which can degrade the temperature rise-characteristics.
As described above, the zigzag arrangement of the heater wires as disclosed in JP-Y2 63-11029 often creates the outstanding state of the heater wires on the covering, making difficult the enhancement in visual quality and operation feel of the steering wheel. On the other hand, the use of a net heating insert obtained by weaving thin heating wires as disclosed in JP-A 4-15162 requires complicated operation of accurately positioning a heater, making difficult a reduction in manufacturing cost. Moreover, prudent assembling is needed not to damage the heater wires, making manufacturing complicated, leading to difficult reduction in manufacturing cost.
It is, therefore, an object of the present invention to provide heaters for heating steering wheels for vehicles, which ensure excellent temperature-rise characteristics and easy assembling with reduced manufacturing cost. Another object of the present invention is to provide steering wheels equipped with heater of the present invention. Still another object of the present invention is to provide a method of manufacturing such steering wheels.
The present invention provides generally a heater for a steering wheel, comprising:
a main body arranged on a rim of the steering wheel, the main body being formed like a net comprising a plurality of heater wires for generating heat upon energization; and
side edges arranged along longitudinal edges of the main body, the side edges being fixed at an inner periphery of the rim.
One aspect of the present invention is to provide a steering wheel, comprising:
a steering-wheel main body with a rim;
a heater arranged on the rim; and
a covering arranged on the heater,
wherein the heater comprises a heater main body formed like a net comprising a plurality of heater wires for generating heat upon energization, and side edges arranged along longitudinal edges of the heater main body and fixed to the covering at an inner periphery of the rim.
Another aspect of the present invention is to provide a method of manufacturing a heater equipped steering wheel, comprising:
placing a heater on a covering of the steering wheel at an inner periphery and along longitudinal edges of the covering to form a tube-like member;
engaging the tube-like member with a rim of the steering wheel at an outer periphery of the rim; and
connecting longitudinal edges of the tube-like member along the inner periphery of the rim.